Stabilities of mixed ligand complexes of Cu(II) with ligands coordinating through O and N : ESR studies

Mixed ligand complexes of Cu(II) with 8-hydroxy-quinolinate (Hy) as one ligand and acetylacetonate (ac.ac) or salicylaldehydate (Sal) as the second ligand have been prepared in reaction mixtures of Cu(Hy)₂ + Cu(ac.ac)₂ and Cu(Hy)₂ + Cu(Sal)₂ in chloroform. Ligand hyperfine structures and the minimum ESR linewidth associated withm = − 3/2 hyperfine component have been used to detect and identify the mixed ligand complexes. The ligands in these complexes coordinate through O or N. The constantsK associated with the ligand exchange equilibriums are ~ 2 at −20°C and are close to the value expected from the empirical relation obtained in an earlier work from a study of Cu(II) complexes in which S also participates in the coordination.